Method and apparatus for detonating radio frequency sensitive blasting caps



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O ou ATTORN( 3,075,461 Patented Jan. 29, 1953 METHOD AND APPARATUS FOR DETONATING RADIO FREQUENCY SENSITIVE BLASTING CAPS Irwin Ehlmann, Hatboro, Pa., assigner of twenty percent to Bilker & Moyerman, Esqs., Philadelphia, Pa., a

partnership Filed Oct. 28, 1960, Ser. No. 65,702 4 Claims. (Cl. 102-1) This invention relates to a method and apparatus for detecting the presence of electrically detonated explosive devices. More particularly, it relates to controlled radio frequency detonation of concealed bombs.

In recent years the nation has been shocked by a series of heinous crimes involving the explosion of bombs aboard commercial airliners. In almost all instances, the perpetrators of these dastardly crimes relied upon electrical detonation devices such as, for instance, electric blasting caps and electric squibs. These devices may be used with simple electric firing systems such as a battery energized circuit including a time delayed switch. Consequently, they are favored as compared to fuses which have to be ignited and burn until the high explosive is reached and detonated.

Detection of a concealed time bomb in passenger luggage has posed an almost insurmountable problem for the air lines. Although it has been done on occasion, the

expedient of opening and examining every piece of lug-A gage going aboard a'plane is time consuming, arouses passenger antagonisrns and is extremely expensive. Yet, no suitable alternate has been discovered or utilized. There is need for an economical, fool-proof and quick system of inspecting luggage for hidden explosives not only to assure passenger safety but also to engender that feeling of psychological security so important to onev traveling aboard an airplane. Obviously, the same system may be used with other common carriers on land, sea or air as well as in the handling of merchandise of all types `by postal authorities and express companies. The

emphasis in this discussion has been placed upon airlines' only because, in the past, they have been a favorite target for these warped personalities.

Consequently, it is an object of this invention to provide a method for detecting the presence of electrically detonated bombs in luggage, said method not requiring that the luggage be opened or visually inspected.

It is also an object of this invention to provide an apparatus which will enable the detection of concealed bombs, of a type utilizing electric squibs or electric blasting caps, in luggage or packages.

Another object of the invention is `to provide a method for detonating bombs, of a type utilizing electric squibs or electric blasting caps, in a controlled environment whereby damage to property will be minimized and hazard to life and limb eliminate Still another object of the invention is to provide an apparatus whereby concealed bombs may be safely exploded without risking human life.

Other objects of the invention include providing quick automatic means for inspecting luggage to determine the presence of hidden bombs therein, said means simultaneously detonating any such devices.

It is also an object of the invention to provide a device of the character described which is simple in operation, economical to produce and eicient in use.

These and other objects of the invention will be apparent to those skilled in the art from the disclosure in the following specification, appended claims and drawings.

In the drawings, wherein like numerals designate like parts:

FIGURE l represents a perspective view, partly brokenaway, of a device embodying my invention.

FIGURE 4 represents a schematic representation of the electronic portions of a device embodying the invention.

Referring now to the drawings, it will be seen that the apparatus includes a sweep frequency generator A, a linear antenna system B, a loop antenna System C, an exposure chamber D, and a conveyor E.

Radio frequency energy from generator A is fed to antenna systems B and/or C which are located within the chamber D. Packages, baggage and the like, being carried through chamber D by conveyor E are subjected to this energy. Any electric blasting caps or electric squibs within the chamber are activated in this manner and the explosive device with which they are associated is consequently detonated.

The exposure chamber D is a long structure, preferably rectangular in cross-section, which is built of materials, such as reinforced concrete, which are adapted to withstand the force of an explosion. Representative dimensions of such a chamber might be as follows: length,y

the construction may be such as to provide a Weak area or safety wall whichwill preferentiallydirect the force of the explosion and prevent any damage to permanentl structure.

Running through the chamber D is a conveyor E.. This conveyor may include a belt 13 and idler rolls 14. Alter-'- natively, if desired, it may be of the gravity Slide or rollertype or even of the air-slide type.- In any event, the

conveyor should be of a type which can be put back intoj operation quickly after an explosion or which is not af-1 fected by an explosion. The conveyor carries baggage, packages and the like from outside of one barrier wally 11, through the opening 12, through the tunnel 10 and` out through the remote barrier wall 11. The conveyor must be constructed so that it is not electrically ground-` ed and obvious expedients would include the use of insulated rolls 14, non-conductive belt 13, etc.

The heart of the 'electronic portion ofthe system, as,

illustrated in FIGURE 4, is a sweep frequency generator A. This is a standard unit which is capable of generating radio energy over a wide and variable range of frequencies. It includes automatic controls for cominually varying the output frequency back and forth over the entire range chosen.l Although any frequency may,l be used from a few kilocycles to as high as 10,000 megacycles, encompassing commercial and amateur broadcast bands as well as low-frequency (i.e. 25-50 megacy-4 cles), high frequency (Le. 148-174 megacycles) and radar frequencies (L8-10,000 megacycles), I prefer to operate my sweep frequency generator in the commercial broadcast band. This band extends from 540 to 1,600 kilocycles. The sweep time is correlated with the speed of the conveyor, an objective being to have an object entering the chamber subjected to at yleast one ascend- 12. The exposure cham-'- ber, within 4which bombs will be detonated, may embodyprinciples of construction well known to those skilled in the art such as are used in powder plants for structures wherein dangerous operations are performed. If desired,-

3 be of the transformer type as shown in FIGURE 4 and provision made to shield the system so as to prevent interference with radio broadcasting.

Two antennae systems are preferred although but a single system Will su'ice if power output is -suciently high. The linear antenna system B comprises a series of spaced-apart (eg. 1) parallel radiators 16 suspended within the tunnel :along its longitudinal dimension. The radiators may be hung from insulators or mounted in any manner whereby they are not electrically grounded and, if desired, may be embedded in .the structure, thus serving simultaneously as reinforcement.v The loop systern C includes va series of closely spaced (eg. 6" apart) loops 17, each of which encircles the conveyor E and generally conforms to the cross-section of the tunnel 10. The antenna systems are tuned so as to be capable of maximum loading by the generator.

A key factor lin the operation of the system is the provision of sufficient electromagnetic energy in the immediate vicinity of the electric detonating device so that its wires can act as an antenna and aow of induced current be created. Induced current in the case of a blasting cap, will be at a maximum when the straight length of the wire (with the cap in the center) is equal to one-half the radio wave length (or a multiple thereof). Current pick up is also maximized when the blasting cap wires are parallel to the transmitting antenna and raised a few feet above ground. The system herein described herein is designed. to meet these desiderata., Induced current within the blasting cap should preferably be in excess of about 0.25 ampere although induced currents of a lesser value may cause firing. For instance, firing conditions would prevail within the standard broadcast range, which is preferred, when the sweep frequency generator has an output of 500 watts and antennae loading is at a minimum of 2 amperes. The conveyor may be run at a speed of, for example, 25 feet per minute and the sweep lfrequency (e.g. S40-1600 k.c.) may be set at about 30 seconds. Thus, were the tunnel 10 approximately 30 feet long, any item on the conveyor would be within immediate proximity of the antennae systems for above about one minute and, consequently, be subjected to at least one full cycle of frequency sweep.

To operate the system one merely places baggage or packages upon the conveyor belt 13 from a position outside of the barrier wall 11. As the baggage is carried through the tunnel 10 it is subjected to one or more transmisson cycles. Electric blastingv caps or squibs will thus be detonated causing, from the criminals point of View, a premature explosion. Conveyor speed, sweep time, transmitter frequency range and power output may all be adjusted to suit particular operating conditions. With sufficient power the antenna systems may be used separately, but it is preferred to use them together.

Although a single embodiment of the invention has been disclosed and described in detail, it is obvious that many changes may be made in size, shape, detail and larrangement of the several elements of the invention, all without departing from the spirit and scope thereof as defined in the appended claims.

Having described my invention, I claim:

1. A method of detonating electric blasting caps capable of having current induced therein by radio frequency energy, said blasting caps being concealed in baggage as an element of a bomb, comprising the steps of establishing an explosion-proof longitudinally extending exposure chamber; providing insulated radio frequency transmitting antennae within said chamber along the length thereof', generating a radio frequency signal of cyclically varying frequency; cycling said radio signal to said trans-v .lated conveyor within said mitting antennae; passing baggage suspected of containing a blasting cap through said exposure chamber adiacent said antennae and insulated from ground, at a fixed rate of travel such that a given piece of baggage remains within Ysaid chamber for at least one full cycle of frequency variation, and inducing Within a blasting cap if present a current sufcient to detonate it.

2. A method of detonating electric blasting caps capa-v ble of having current induced therein by radio frequency energy, said blasting caps being concealed in baggage as an element of a bomb, comprising the steps of establisliing a longitudinally extending, explosion-proof 'tunnellike exposure chamber; providing a plurality of insulated radiating antennae within said chamber including a longitudinally extending linear antenna and transversely positioned loop antennae; generating a sweep radio frequency signal which sweeps at a uniform rate from 540 to 1600 kilocycles and back; feeding said'radio frequency' signal to said antennae', passing baggage suspected or containing a blasting cap through said exposure chamber parallel to said linear antenna and through said loop antennae, and insulated from ground, at a fixed rate of longitudinal travel such that a given piece of baggage remains within said chamber for at least one full cycle of frequency sweep, and inducing within a blasting cap if present a detonation current of at least 0.25 ampere 3. An apparatus foidetonating electric blasting caps capable of having current induced therein by radio frequencyrenergy, said blasting caps being concealed in baggage as an element of a bomb, comprising an explosionproof exposure chamber containing an internal tunnel extending longitudinally therethrough; an electrically insutunnel to carry baggage from one end thereof to the other; an electrically insulated radiating antenna system within said tunnel; a sweep radio frequency generator; coupler means for feeding the output of said generator to said antenna system; the radio frequency energy radiated by said antenna system, when baggage is within `said tunnel for one full cycle of frequency variation, inducing within a blasting cap if present a current suicient to detonate it.

4. An apparatus for detonating concealed electric blasting-caps capable of having current induced therein by radio frequency energy, said blasting caps being concealed in baggage as an element of a bomb, comprising a longitudinally extending explosion-proof chamber containing an internal tunnel; an electrically insulated explo# sion resistant conveyor for carrying luggage through the length of said tunnel; a plurality of electrically insulated radiating antennae within said tunnel including longitudinally extending linear antennae paralleling said conveyor and longitudinally spaced transverse loop antennae encircling said conveyor; a sweep frequency generator which generates a radio frequency signal ranging back and forth from 540 to 1600 kilocycles; a coupler for electrically loading said antennae with the output of said generator;

the radio frequency energy radiated by said antenna, when said baggage is within said tunnel for one cycle of frequency variation, inducing within said blasting cap present a current suicient to detonate it.

References Cited in the tile of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE EE 'TIIICATE @E C ECTION Patent No 3,075,461 January 29, 1963 Irwin EhImann It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line 59, for "saidn read --f any Signed and sealed this 20th day of August 1963o (SEAL) Attest:

ERNEST w. SWIDER DAVID L. LADD Attestilg ffl Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No 3,075,461 January 29, 1963 Irwin Ehlmann It s hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line 59, for "said" read n any Signed and sealed this 20th day of August 1963i,

(SEAL) Attest:

rERNEST w. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

1. A METHOD OF DETONATING ELECTRIC BLASTING CAPS CAPABLE OF HAVING CURRENT INDUCED THEREIN BY RADIO FREQUENCY ENERGY, SAID BLASTING CAPS BEING CONCEALED IN BAGGAGE AS AN ELEMENT OF A BOMB, COMPRISING THE STEPS OF ESTABLISHING AN EXPLOSION-PROOF LONGITUDINALLY EXTENDING EXPOSURE CHAMBER; PROVIDING INSULATED RADIO FREQUENCY TRANSMITTING ANTENNAE WITHIN SAID CHAMBER ALONG THE LENGTH THEREOF; GENERATING A RADIO FREQUENCY SIGNAL OF CYCLICALLY VARYING FREQUENCY; CYCLING SAID RADIO SIGNAL TO SAID TRANSMITTING ANTENNAE; PASSING BAGGAGE SUSPECTED OF CONTAINING A BLASTING CAP THROUGH SAID EXPOSURE CHAMBER ADJACENT SAID ANTENNAE AND INSULATED FROM GROUND, AT A FIXED RATE OF TRAVEL SUCH THAT A GIVEN PIECE OF BAGGAGE REMAINS WITHIN SAID CHAMBER FOR AT LEAST ONE FULL CYCLE OF FREQUENCY VARIATION, AND INDUCING WITHIN A BLASTING CAP IF PRESENT A CURRENT SUFFICIENT TO DETONATE IT. 